At CES, General Motors announced that it will open its OnStar ATOMS (Advanced Telematics Operating System) cloud server to selected developers in this year’s first half.

The first third-party app will be RelayRides, a peer-to-peer service in which users rent their cars to other drivers. It also will be available on Android and iOS platforms. It’s an idea that makes many people nervous, Forbes points out. A similar venture, HiGear, shut down last year after repeated thefts. (On the other hand, Zipcar has found more success with its 9,000 vehicles owned by the company.)

OnStar, though, has the ability to track vehicles and gently shut them down. RelayRides offers a $1 million liability policy and peer-to-peer vetting, which might make the idea more palatable.

Beyond its emergency and navigation services, OnStar is also looking at incorporating Verizon 4G LTE into vehicles as part of a subscription. GM’s demo showed the ability to use Skype or play Angry Birds from the back seat.

GM’s press release quotes OnStar President Linda Marshall as saying:

Research shows that the amount of mobile applications for the Android and iOS platforms is likely to double in the next 12 months. Customer demand is driving a new marketplace for a variety of automotive applications.

With this step we believe we can broaden our portfolio, grow our business and enable our customers to achieve additional functionality from their vehicle using their computer, smartphone, tablet or other devices.

Meanwhile, Ford plans to open a Silicon Valley office this spring to explore new ways to connect drivers to the Internet, and to other drivers. GM already has an outpost there, as do the Renault-Nissan Alliance, BMW and Volkswagen. More details about the 15-person lab are expected to be announced soon.